1. Technical Field
Various embodiments of the present invention relate to a magnetic head and a tape drive for reading and writing data to magnetic storage media.
2. Background Art
Storage of data in a secure and retrievable manner has continually developed. Data such as technical, financial, and other information is desired to be stored inexpensively, but also such that it can be retrieved or read months or years after storage such as to allow a company to store data that is not required to be regularly accessible, or to recover from a loss of data caused by a natural disaster or technical failure. To this end, the data storage industry often stores data on disk or optical media for short term data storage; and to magnetic tape or tape cartridges for long term storage or for archiving. It is desirable for the data or information on archived tape cartridges to be accessible or readable for many years. Each company or enterprise may use large numbers of tape cartridges to store data, and as a result, some companies' largest expense associated with data backup and archiving is the storage media itself, and not the tape drives and equipment used to access the tape cartridges.
An ongoing problem in the data storage industry is the development of advances in data storage technology such as tape drive technology, while allowing data storage customers to continue to use their existing libraries of tape cartridges. For example, magnetic read/write heads are used to read data from tape and to write data to tape. There is continued market demand to increase the amount of data that can be written to the same amount of tape, to increase data density on a tape cartridge. One approach to achieve this goal is to reduce the width of the write elements used to write data and more tightly place write elements on the head. The read elements then are also reduced in size to read the narrower tracks of data on the tape surfaces. Unfortunately, these new and narrower read elements often cannot effectively read data written by older or “legacy” heads (or legacy tape drives). A further complication is that code and circuitry that is used to write and to read the data on the tapes, e.g., the recording and read channels, are also changing rapidly. Hence, a new and improved tape drive may include a new read channel that is matched with the drive's recording channel, but this may result in the new tape drive being unable to read data written with a predecessor or legacy tape drive that included a predecessor or legacy recording channel. In other words, each generation of tape drive are utilized differing recording and/or read channels to store data to, and retrieve data from the tape; and these channels often are not wholly compatible.
Compatibility issues between current and predecessor formats may be considered or labeled a lack of backward read capability or legacy read capability, which may be desired to support media reuse. Media reuse protects a user's investments in media and automation infrastructure (e.g., tape library systems and equipment for particular tape cartridges). Reuse is the “reclaiming” of tapes or other media that may have been written by a legacy drive or a more advanced drive; and these reclaimed tapes are rewritten by a different drive that may be advanced, or not, relative to the original drive. Backward reading capability also improves data migration and efficiency and helps reduce the cost of converging media to higher capacity formats of the latest generation tape drives. Unfortunately, backward read capability has proven difficult to provide as customers have tape in their libraries that was written by the prior generation of tape drive and head technology, as well as tape, that was written by drives belonging to much earlier generations (e.g., it is not uncommon for a single customer to have cartridges from four or more generations of tape drives). Testing has indicated that using newer, typically narrower read elements with prewritten tapes provides typically poor to bad results based on detected data error rates, and effectiveness of the newer heads generally decreases over time as wear occurs, such as wear due to pole tip recession. Backward read capabilities of new drives are also reduced in some situations when a read channel is configured for a particular tape surface, e.g., burnished or smoother surfaces versus rough media. Presently, the solutions typically involve maintaining legacy drives for use with legacy tapes (or for recovery operations if the legacy tapes need to be used) and/or by employing a costly and time-consuming migration of data from the legacy tapes to new media, with the legacy tapes being eventually discarded.